1. Field of the Invention
This invention relates to a semiconductor light-emitting device, and particularly to a light-emitting device using a vacuum doughnut to serve as a current blocking layer.
2. Description of Prior Art
Generally speaking, light-emitting diodes that are characterized by a double heterojunction have low luminous efficiencies because of contact shadowing caused by current crowding at the p-n junction of the diode under the contact area. Referring to FIG. 1, a conventional light-emitting diode comprises a substrate 10, a buffer layer 12, a double heterostructure 14, a cap layer 16 and metal contacts 18a and 18b. As external contact is made to the structure through the metal contact 18b, light is emitted along the double heterostructure 14. However, the light emitted along the double heterostructure 14 under the contact 18b is absorbed or reflected by the contact, which in effect acts as a shadow to a portion of the light being emitted from the entire double heterostructure, thus reducing the total external light output. Therefore, in order to increase the output of the light being emitted along the entire double heterostructure of the diode, it is essential to minimize contact shadowing beneath the contact area.